Large scale emergency situations are an unfortunate reality of today's world. Whether the result of an accident or an intentional act, when an explosion, building collapse, terrorist attack, or a similar event occurs, many people in the immediate area may be affected. Those who respond first to such events have a need to determine how many people are involved, and where those people may be located. This is very difficult in today's mobile society. There is currently no simple way to determine who may have been in a building when it collapsed or at the scene of an explosion. Any information that would indicate the potential presence of survivors or victims in an area may be helpful to emergency response authorities. Such information may guide first responders in planning how to address the situation and allocate resources. Such information may also be helpful to family members and others concerned about people who may have been involved in the situation.